Fig. 5. Classes of mutants affecting the localisation of both oskar and bicoid mRNA. In situ hybridisations for bicoid are shown on the left (A,C,E,G) and hybridisations for oskar are shown on the right (B,D,F,H). (A,B) Wild-type egg chambers. (C,D) boussole^8F8-6. This mutant shows ectopic localisation of oskar mRNA to the centre of the oocyte, and posterior accumulation of bicoid mRNA in a subset of oocytes. (E,F) abruzzi^7C3-10 is a member of a large class of mutants, in which the oocyte nucleus is frequently mislocalised (see arrow in panel E) and bicoid mRNA associates with the cortex proximal to the nucleus. In these mutants, oskar mRNA also fails to adopt a wild-type localisation pattern. (G,H) mertz⁸⁰⁷⁷, an example of the class of mutants in which both oskar and bicoid mRNAs fail to localise to their respective poles and are diffuse in the oocyte.